Synthesis of Trifluoromethylated Sultones from Alkenols Using a

Jun 21, 2016 - *E-mail: [email protected]. This article is part of the ... Thomas RawnerEugen LutskerChristian A. KaiserOliver Re...
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Synthesis of Trifluoromethylated Sultones from Alkenols Using a Copper Photoredox Catalyst Thomas Rawner, Matthias Knorn, Eugen Lutsker, Asik Hossain, and Oliver Reiser* Institut für Organische Chemie, Universität Regensburg, Universitätsstr. 31, 93053 Regensburg, Germany S Supporting Information *

ABSTRACT: A photo-redox-catalyzed procedure for the onestep formation of sultones from α,ω-alkenols and trifluoromethylsulfonyl chloride is described. Using [Cu(dap)2]Cl (1 mol %), a wide range of substrates can be cleanly converted to the target compounds, while commonly employed photoelectron transfer catalysts such as [Ru(bpy)3]Cl2 or facIr(ppy)3 fail in this transformation. The obtained fluorinated sultones are attractive as potential electrolyte additives or as structural motifs in drug synthesis, with the latter being demonstrated with the synthesis of a trifluoroethyl-substituted analogue of a benzoxathiin that has high anti-arrhythmic activity.

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INTRODUCTION Since the discovery of internal esters of hydroxysulfonic acids, commonly known as “sultones”, by Erdmann in 1888,1 this compound class has been attractive for a variety of research fields including natural product synthesis and biologically active compounds, medicinal chemistry, and material science.2 For instance, Metz et al.3 could successfully demonstrate the application of sultones as key intermediates in natural product synthesis. Moreover, promising results against human immunodeficiency virus type 1 (HIV-1), human cytomegalovirus (HCMV), and varicellazoster virus (VZV) were demonstrated by Velázquez and co-workers.4 Furthermore, sultones are applied in lithium-ion batteries (LIB) as an electrolyte additive5 to overcome problems like low temperature and calendar life performance and safety issues for their application in electric vehicles. Especially in this context, the virtue of fluorine-containing sultone additives has been recognized.6 Early approaches for sultone syntheses utilized the sulfonation of olefins with SO3 and its adducts,7 carbanion-mediated sulfonate coupling reactions,8 or heating of the corresponding hydroxysulfonic acids in vacuum.9 In the past decade, milder methodologies have been developed including ring-closure metathesis (RCM),10 Diels−Alder reactions,11 or rhodium-catalyzed C−H insertions.12 The incorporation of fluorinated moieties, particularly the trifluoromethyl (CF3) group, into organic compounds and transition metal complexes can profoundly change their chemical, physical, and biological properties.13 Consequently, various approaches including nucleophilic,14 electrophilic,15 and radical16 strategies for installing a CF3 moiety into organic molecules have been reported. In recent years, rapid progress was made in the field of visible-light-mediated photoredox catalysis, which has established itself as a powerful technique for conducting free-radical © 2016 American Chemical Society

Scheme 1. Visible-Light-Mediated [Cu(dap)2]Cl-Catalyzed Intramolecular Atom Transfer Radical Addition Processes

transformations.17 In this context, the visible-light-induced photocatalytic difunctionalization of alkenes proved to be an efficient approach for CFxR-containing heterocycles.18 Recently, a variety of pyrrolidines and lactones were efficiently synthesized by photoredox catalysis employing [Cu(dap)2]Cl (dap = 2,9-di(p-anisyl)-1,10-phenanthroline) and CHF2SO2Cl, as demonstrated by Dolbier and co-workers (Scheme 1).19 In this case, however, the reaction proceeds with loss of sulfur dioxide without any sign of sultone or sulfamide formation. Special Issue: Photocatalysis Received: April 30, 2016 Published: June 21, 2016 7139

DOI: 10.1021/acs.joc.6b01001 J. Org. Chem. 2016, 81, 7139−7147

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The Journal of Organic Chemistry

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RESULTS AND DISCUSSION Following our interest in photocatalysis20 and especially the application of environmentally benign copper complexes21,22 for visible-light photoredox catalysis, we investigated the copper-catalyzed visible-light reaction of CF3SO2Cl with terminal alkenes.21 [Cu(dap)2]Cl was identified as a unique catalyst that, in contrast to other photoredox catalysts,23 gives rise to a net addition of a trifluoromethyl and a chlorosulfonyl group to the alkene. Expanding the scope of this transformation, we report herein the one-step visible-light-mediated synthesis of α-substituted trifluoromethylated sultones from α,ω-alkenols. Using pent-4-en-1-ol (3c) as a benchmark substrate, we were delighted to find that in the presence of [Cu(dap)2]Cl (1 mol %) the reaction with triflyl chloride (CF3SO2Cl) indeed results in the smooth formation of sultone 4c (Table 1, entry 1). Omitting the base, which is assumed to act as a

higher light energy, we also tested [Cu(dap)2]Cl at this wavelength, which proceeded cleanly but resulted in a slightly lower yield of 4c (entry 13). With optimized conditions in hand, we examined the scope of the reaction (Table 2). Attempts to use allyl alcohol 3a Table 2. Substrate Scope of Photo-redox-Catalyzed Intramolecular Formation of Sultonea

Table 1. Optimization of Reaction Parameters for the Sultone Formationa

entry

catalyst

solvent

yield (%)

1 2b 3 4 5 6c 7d 8 9 10 11e 12e 13e

[Cu(dap)2]Cl [Cu(dap)2]Cl [Cu(dap)2]Cl [Cu(dap)2]Cl [Cu(dap)2]Cl [Cu(dap)2]Cl [Cu(dap)2]Cl CuCl no catalyst dap [Ru(bpy)3]Cl2 fac-Ir(ppy)3 [Cu(dap)2]Cl

MeCN MeCN CH2Cl2 DMF DMSO MeCN MeCN MeCN MeCN MeCN MeCN MeCN MeCN

88 34 71 50 61 49 4 2 nr nr 10 18 66

a Reaction conditions: 4-penten-1-ol 3c (0.5 mmol, 1.0 equiv), CF3SO2Cl (1.0 mmol, 2.0 equiv), K2HPO4 (1.0 mmol, 2.0 equiv), catalyst (1.0 mol %) in solvent (1.5 mL), irradiation at 530 nm (green LED) for 17 h. All yields are based on using benzotrifluoride as the internal standard. bAbsence of K2HPO4. cCatalyst loading 0.5 mol %. d Dark reaction. eIrradiation at 455 nm (blue LED).

scavenger for HCl that is formed in the course of the reaction, leads to a significant decrease in yield (entry 2). While the reaction proceeds well in CH2Cl2, DMF, or DMSO (entries 3−5), acetonitrile appears to be the optimal solvent (entry 1). Reducing the amount of [Cu(dap)2]Cl to 0.5 mol % (entry 6) was met with a reduction in yield: we reason that this is not a result of catalyst deactivation but rather due to deep coloring of the reaction solution with time that blocks the photoprocess. In contrast, net addition of CF3Cl was mainly observed besides unidentified side products and low yields of 4c when well-established photoredox catalysts such as [Ru(bpy)3]Cl2 (bpy = 2,2′-bipyridyl) or fac-Ir(ppy)3 (ppy = 4-pyrrolidinopyridine) were used (entries 11 and 12). These photocatalysts require irradiation at 455 nm. To rule out that the failure to form 4c with these catalysts was due to the

a Reaction conditions: alkene 3 (1.0 mmol, 1.0 equiv), CF3SO2Cl (2.0 mmol, 2.0 equiv), K2HPO4 (2.0 mmol, 2.0 equiv), [Cu(dap]2Cl (1.0 mol %) in MeCN (3.0 mL), irradiation at 530 nm (green LED) for 17 h. bDiastereomeric ratio of 4i syn/anti = 44:56. cDiastereomeric ratio of 4k syn/anti = 43:57.

gave rise to a complex reaction mixture with only trace amounts of the desired β-sultone 4a detectable (entry 1), a compound class that is known to have low stability.24 The γand δ-sultones 4b and 4c were obtained in good to excellent yields, while a drop in yield was observed for ε-sultone 4d (entries 2−4). To demonstrate the viability of the method for preparative purposes, scale-up of 4b and 4c to gram quantities 7140

DOI: 10.1021/acs.joc.6b01001 J. Org. Chem. 2016, 81, 7139−7147

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The Journal of Organic Chemistry Scheme 2. Various Sulfonyl Chlorides Tested for Sultone Synthesisa

a

For conditions, see Table 2.

Scheme 3. Synthesis of Novel Benzoxathiin Derivative Derived from Visible-Light-Mediated Intramolecular Formation of Sultone as the Key Stepa

a

Reaction conditions: (a) 2-allyl-6-methoxyphenol 3m (1.0 equiv), CF3SO2Cl (2.0 equiv), K2HPO4 (2.0 equiv), [Cu(dap)2]Cl (1.0 mol %), MeCN, irradiation at 530 nm (green LED), rt, 24 h, 64%; (b) HBr (47 wt %), 140 °C, 3 h, 99%; (c) epichlorohydrin (18.2 equiv), K2CO3 (2.2 equiv), anhydrous acetone, reflux, 2 days, 65% (dr = 50:50); t-BuNH2, anhydrous MeOH, reflux, 2 h, 49% (20% overall yield after four steps).

increasing amounts of CF3Cl addition, which is the general reaction mode for ruthenium- or iridium-based photocatalysts. An X-ray structure of 4f confirmed the general structure of the sultones formed. Embedding a phenol moiety into the substrate was also possible, as demonstrated with the transformation of 3j to 4j, which is especially relevant for the synthesis of drug-like sultones (vide infra). Next, different commercially available sulfonyl chlorides were tested for the introduction of various side chains (Scheme 2). Indeed, cyclization was observed for alkenols 3c

was also demonstrated (see Supporting Information). Focusing on δ-sultones, readily available pent-4-en-1-ols 3e− 3k being substituted in the 2- and/or 3-position gave rise to sultones 4e−4k; however, methyl or phenyl substitution either in the 4- or 5-position led to complex reaction mixtures containing regio- and diastereomeric sultones, and in addition, trifluoromethylchlorination of the alkene was observed. In general, it should be noted that the trifluoromethylchlorosulfonylation of alkenes developed by us is sensitive to steric effects: substitution at the double bond or next to it leads to 7141

DOI: 10.1021/acs.joc.6b01001 J. Org. Chem. 2016, 81, 7139−7147

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The Journal of Organic Chemistry Scheme 4. Mechanistic Studies: Trifluoromethylchlorosulfonylation versus Triflate Formation

While the overall process to sultones 4 proceeded cleanly, we identified as minor impurities (500 mg/kg in stomach).25 Considering the benefits of fluoroalkyl group introduction into biologically active molecules,26 based on the methodology reported here, the CF3CH2 analogue 10 could be efficiently synthesized in only four steps from commercially available oeugenol 3m (Scheme 3). The latter was converted under the standard conditions to sultone 4m on a 3 mmol scale in 64% yield. Cleavage of the methoxy group with HBr and etherification with racemic epichlorohydrine gave rise to 9, which upon treatment with tert-butylamine resulted in 10 as a 1:1 mixture of diastereomers in an overall yield of 20% over four steps. In order to gain a deeper insight into the mechanism, a series of experiments were carried out (Scheme 4). Taking 3c as a model compound, we tested if initially trifluorochlorosulfonylation to 13c followed by cyclization takes place or if the triflate 12 is formed first, which is subsequently photochemically cleaved with concurrent cyclization to 4c. The latter was ruled out by the independent synthesis of 12, which resulted upon irradiation under the standard reaction conditions only in polymerization of the starting material.27 Moreover, the reaction of 3c with CF3SO2Cl is sluggish, even in the presence of a base such as pyridine. We therefore conclude that trifluoromethylsulfonylation of the alkene precedes sultone formation. In agreement with these findings, reacting 14 under the reaction conditions, trifluoromethylsulfonylation to 15 was observed (Scheme 5).

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Scheme 5. Trifluoromethylchlorosulfonylation of Protected α,ω-Alkenol 14

CONCLUSION In conclusion, we have described a simple photo-redoxcatalyzed procedure for the one-step synthesis of sultones 4a− 4m with trifluoroethyl substitution in the 3-position30 from readily available α,ω-alkenols 3a−3m in moderate to excellent yield using an inexpensive copper catalyst with low loading. The resulting sultones might have potential as lithium battery 7142

DOI: 10.1021/acs.joc.6b01001 J. Org. Chem. 2016, 81, 7139−7147

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The Journal of Organic Chemistry Scheme 6. Proposed Mechanism

or by column chromatography on silica gel to yield the desired product. General Procedure for the Scale-Up of Sultones (GP-B). The reactions were performed 10 times on a 5 mmol scale (=50 mmol). An oven-dried Schlenk tube equipped with a magnetic stirring bar was charged with alcohol (5.0 mmol, 1.0 equiv), [Cu(dap)2]Cl (44 mg, 5.0 μmol, 1.0 mol %), and K2HPO4 (1.76 g, 10.0 mmol, 2.0 equiv) in anhydrous MeCN (15 mL). The resulting suspension was degassed by three freeze−pump−thaw cycles followed by the addition of CF3SO2Cl (1.1 mL, 10.0 mmol, 2.0 equiv). The reaction mixture was irradiated under stirring for 48 h with a green light plate (LED, λmax = 530 nm) at room temperature. The combined reaction solution of the overall 10 reactions was filtered through a silica plug with CH2Cl2 as the eluent and concentrated in vacuo. The residue was purified by distillation under reduced pressure to yield the desired product. 3-(2,2,2-Trifluoroethyl)-1,2-oxathiolane 2,2-dioxide 4b. Following GP-A, 4b was prepared using but-3-en-1-ol 3b (86 μL, 1.0 mmol, 1.0 equiv), [Cu(dap)2]Cl (8.8 mg, 1.0 μmol, 1.0 mol %), K2HPO4 (352 mg, 2.0 mmol, 2.0 equiv), and CF3SO2Cl (210 μL, 2.0 mmol, 2.0 equiv) in anhydrous MeCN (3 mL). The reaction solution was filtered through a silica plug with CH2Cl2 as the eluent. The filtrate was concentrated under reduced pressure to afford 4b as a colorless oil (102 mg, 50%). Following GP-B, 4b was prepared using but-3-en1-ol 3b (430 μL, 5.0 mmol, 1.0 equiv), [Cu(dap)2]Cl (44 mg, 5.0 μmol, 1.0 mol %), K2HPO4 (1.76 g, 10.0 mmol, 2.0 equiv), CF3SO2Cl (1.1 mL, 10.0 mmol, 2.0 equiv), and anhydrous MeCN (15 mL). The residue was purified by distillation under reduced pressure (1.4 mbar, oil bath temperature 150−170 °C, boiling point at 87−89 °C) to yield 4b as a colorless oil (4.88 g, 48%): Rf = not determinable; staining = not determinable (UV inactive); 1H NMR (600 MHz, CDCl3) δ = 4.51 (ddd, J = 9.2, 8.2, 3.3 Hz, 1H), 4.43 (td, J = 9.1, 7.0 Hz, 1H), 3.50 (tdd, J = 10.1, 7.9, 3.9 Hz, 1H), 2.95− 2.87 (m, 1H), 2.83−2.78 (m, 1H), 2.51−2.41 (m, 2H); 19F NMR (282 MHz, CDCl3) δ = −64.99 (s, 3F); 13C NMR (75 MHz, CDCl3) δ = 125.3 (d, JC−F = 277.1 Hz), 67.2, 49.7 (q, JC−F = 2.8 Hz), 33.5 (q, JC−F = 30.8 Hz), 29.6; IR (neat, cm−1) 2966, 2926, 1350, 1315, 1258, 1165, 1137, 1077, 993, 914, 792, 661, 631, 609, 496; HRMS (APCI) exact mass calcd for C5H8F3O3S m/z 205.0141, found m/z 205.0140 [M + H]+; GC analysis, purity 94%, tR = 5.491 min, wt(H2O) = 407 ppm. 3-(2,2,2-Trifluoroethyl)-1,2-oxathiane 2,2-dioxide 4c. Following GP-A, 4c was prepared using pent-4-en-1-ol 3c (102 μL, 1.0 mmol, 1.0 equiv), [Cu(dap)2]Cl (8.8 mg, 1.0 μmol, 1.0 mol %), K2HPO4 (352 mg, 2.0 mmol, 2.0 equiv), and CF3SO2Cl (210 μL, 2.0 mmol, 2.0 equiv) in anhydrous MeCN (3 mL). The reaction solution was filtered through a silica plug with CH2Cl2 as the eluent. The filtrate

additives, which is currently under investigation. Moreover, the trifluoroethyl-substituted benzoxathiin derivative 10 could be synthesized, which is an analogue of the highly potent βblocker 11.

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EXPERIMENTAL SECTION

General Information. All reactions were performed in flamedried flasks under N2 atmosphere using anhydrous solvents unless otherwise stated. Anhydrous solvents were prepared by established laboratory procedures. The commercially available chemicals were purchased in high quality and were used without further purification. All reactions were monitored by thin layer chromatography (TLC). Visualization was done with UV light (λ = 254 nm) and staining with vanillin (6 g of vanillin in 100 mL of EtOH and 5 mL of H2SO4), sodium permanganate (1 g of KMnO4 and 2 g of Na2CO3 in 100 mL of H2O), PMA (1 g of ceric ammonium sulfate and 2.5 g of ammonium molybdate in 10 mL of H2SO4 and 90 mL of H2O), or anisaldehyde (5 mL of p-anisaldehyde in 5 mL of H2SO4 and 100 mL of EtOH) followed by heating. All NMR spectra were recorded in CDCl3 unless otherwise stated. Chemical shifts δ are reported in parts per million (ppm) relative to the signal of CDCl3 (7.26 ppm for 1H, 77.16 ppm for 13C). High-resolution mass spectra were measured using electrospray ionization (ESI) or atmospheric pressure chemical ionization (APCI) with a quadrupole time-offlight (Q-TOF) detector. The following compounds were synthesized according to the reported procedures, and the spectroscopical data are consistent with those reported: 2-methylhex-5-en-2-ol 3e,31 2,2diphenylpent-4-en-1-ol 3f, 32 diethyl-2-allyl-2-(hydroxymethyl)malonate 3g,33 (1-allylcyclohexyl)methanol 3h,34 rel-(1R,6S)-7oxabicyclo[4.1.0]heptane,35 rel-(1S,2R)-2-allylcyclohexan-1-ol 3i,36 1phenylpent-4-en-1-ol 3k,37 pent-4-en-1-yl trifluoromethanesulfonate 12,38 2-(chloromethyl)tetrahydrofuran,39 and 5-methoxypent-1-ene 14.40 General Procedure for the Sultone Formation (GP-A). An oven-dried Schlenk tube equipped with a magnetic stirring bar was charged with alkene 3 (1.0 mmol, 1.0 equiv), [Cu(dap)2]Cl (8.8 mg, 1.0 μmol, 1.0 mol %), and K2HPO4 (348 mg, 2.0 mmol, 2.0 equiv) in anhydrous MeCN (3 mL). The resulting suspension was degassed by three freeze−pump−thaw cycles followed by the addition of triflyl chloride (210 μL, 2.0 mmol, 2.0 equiv). The reaction mixture was irradiated under stirring for 17 h with a green light optical fiber (LED, λmax = 530 nm) at room temperature. The reaction mixture was quenched with water (3 mL), and the product was extracted with CH2Cl2. The combined organic layers were dried over anhydrous Na2SO4 and concentrated in vacuum. The residue was purified by filtration through a silica plug with CH2Cl2 as the eluent 7143

DOI: 10.1021/acs.joc.6b01001 J. Org. Chem. 2016, 81, 7139−7147

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The Journal of Organic Chemistry

2.6 Hz), 32.4 (q, JC−F= 30.5 Hz); IR (neat, cm−1) 3064, 3030, 2960, 2874, 1739, 1603, 1495, 1448, 1361, 1316, 1260, 1174, 1141, 1014, 954, 928; HRMS (ESI) exact mass calcd for C18H17F3O3S m/z 370.0845, found m/z 370.0847 [M]+; mp 187−193 °C. Diethyl 3-(2,2,2-Trifluoroethyl)-1,2-oxathiane-5,5-dicarboxylate 2,2-dioxide 4g. Following GP-A, 4g was prepared using diethyl 2allyl-2-(hydroxymethyl)malonate 3g (230 mg, 1.0 mmol, 1.0 equiv), [Cu(dap)2]Cl (8.8 mg, 1.0 μmol, 1.0 mol %), K2HPO4 (352 mg, 2.0 mmol, 2.0 equiv), and CF3SO2Cl (210 μL, 2.0 mmol, 2.0 equiv) in anhydrous MeCN (3 mL). Chromatography on silica gel (pentane/ CH2Cl2, 5:1) afforded 4g as a colorless oil (181 mg, 50%): Rf (pentane/CH2Cl2, 5:1) = 0.42; staining = KMnO4 (UV inactive); 1H NMR (600 MHz, CDCl3) δ = 5.01−4.88 (m, 2H), 4.40−4.20 (m, 4H), 3.84−3.75 (m, 1H), 3.20−2.88 (m, 2H), 2.43−2.22 (m, 2H), 1.34−1.25 (m, 6H); 19F NMR (282 MHz, CDCl3) δ = −63.57 (s, 3F); 13C NMR (75 MHz, CDCl3) δ = 166.9, 166.3, 125.2 (q, JC−F = 277.7 Hz), 74.5, 63.2, 63.1, 57.1, 50.7 (q, JC−F = 2.2 Hz), 39.9, 34.1, 32.7 (q, JC−F = 31.0 Hz), 14.0; IR (neat, cm−1) 2989, 1733, 1439, 1368, 1320, 1252, 1178, 1141, 1014, 965, 846, 801, 742, 697; HRMS (ESI) exact mass calcd for C12H18F3O7S m/z 363.0720, found m/z 363.0721 [M + H]+; GC analysis, purity 88%, tR = 11.933 min. 4-(2,2,2-Trifluoroethyl)-2-oxa-3-thiaspiro[5.5]undecane 3,3-Dioxide 4h. Following GP-A, 4h was prepared using (1-allylcyclohexyl)methanol 3h (154 mg, 1.0 mmol, 1.0 equiv), [Cu(dap)2]Cl (8.8 mg, 1.0 μmol, 1.0 mol %), K2HPO4 (352 mg, 2.0 mmol, 2.0 equiv), and CF3SO2Cl (210 μL, 2.0 mmol, 2.0 equiv) in anhydrous MeCN (3 mL). Chromatography on silica gel (pentane/CH2Cl2, 1:1) afforded 4h as a yellowish oil (213 mg, 74%): Rf (pentane/CH2Cl2, 2:1) = 0.40; staining = PMA (UV inactive); 1H NMR (600 MHz, CDCl3) δ = 4.35 (d, J = 11.4 Hz, 1H), 3.47 (ddt, J = 13.4, 10.3, 3.5 Hz, 1H), 2.90 (dqd, J = 15.3, 11.0, 2.9 Hz, 1H), 2.42−2.24 (m, 2H), 1.86− 1.31 (m, 12H); 19F NMR (376 MHz, CDCl3) δ = −64.00 (s, 3F); 13 C NMR (101 MHz, CDCl3) δ = 125.5 (q, JC−F = 277.4 Hz), 80.7, 49.7 (q, JC−F = 2.7 Hz), 39.4, 34.2, 33.9, 32.9 (q, JC−F = 30.4 Hz), 30.5, 26.0, 21.4, 20.9; IR (neat, cm−1) 2933, 2863, 1454, 1361, 1320, 1267, 1170, 1003, 954, 910, 846, 805, 731; HRMS (ESI) exact mass calcd for C11H18F3O3S m/z 287.0923, found m/z 287.0928 [M + H]+; GC analysis, purity 88%, tR = 11.433 min. rel-(4aR,8aS)-3-(2,2,2-Trifluoroethyl)octahydrobenzo[e][1,2]oxathiine 2,2-Dioxide 4i. Following GP-A, 4i was prepared using rel(1S,2R)-2-allylcyclohexan-1-ol 3i (140 mg, 1.0 mmol, 1.0 equiv), [Cu(dap)2]Cl (8.8 mg, 1.0 μmol, 1.0 mol %), K2HPO4 (352 mg, 2.0 mmol, 2.0 equiv), and CF3SO2Cl (210 μL, 2.0 mmol, 2.0 equiv) in anhydrous MeCN (3 mL). The reaction solution was filtered through a silica plug with CH2Cl2 as the eluent. The filtrate was concentrated under reduced pressure to afford 4i as a mixture of diastereomers as a yellowish oil (245 mg, syn/anti = 44:56, 90% overall yield): Rf = not determinable; staining = not determinable (UV inactive); 1H NMR (600 MHz, CDCl3) δ = 4.38−4.29 (m, 2H), 3.53−3.48 (m, 1H), 3.38 (ddt, J = 12.3, 7.0, 3.3 Hz, 1H), 2.91−2.87 (m, 1H), 2.62 (dd, J = 10.2, 5.1 Hz, 1H), 2.36−2.31 (m, 1H), 2.26−2.18 (m, 2H), 2.06 (ddt, J = 16.4, 8.3, 3.6 Hz, 3H), 1.84 (q, J = 3.2 Hz, 2H), 1.81−1.66 (m, 8H), 1.56−1.48 (m, 2H), 1.30− 1.22 (m, 4H), 1.14−1.04 (m, 2H); 19F NMR (376 MHz, CDCl3) δ = −63.53 (s, 3F, minor), −64.42 (s, 3F, major); 13C NMR (101 MHz, CDCl3) δ = 125.6 (q, JC−F = 277.3 Hz), 125.5 (q, JC−F = 277.4 Hz), 89.2, 89.0, 54.2 (q, JC−F = 2.5 Hz), 52.0 (q, JC−F = 2.4 Hz), 40.7, 35.4, 34.7, 32.4, 32.8 (q, JC−F = 30.5 Hz), 32.0 (q, JC−F = 30.0 Hz), 31.6, 31.5, 30.2, 30.0, 24.9, 24.7, 24.0, 23.9; IR (neat, cm−1) 2941, 2866, 1454, 1357, 1256, 1137, 977, 910, 883, 831, 753, 667; HRMS (APCI) exact mass calcd for C10H19F3NO3S m/z 290.1032, found m/z 290.1036 [M + NH4]+; GC analysis, purity 90%, tR = 10.853 min (two diastereomers). 3-(2,2,2-Trifluoroethyl)-3,4-dihydrobenzo[e][1,2]oxathiine 2,2-Dioxide 4j. Following GP-A, 4j was prepared using 2-allylphenol 3j (134 mg, 1.0 mmol, 1.0 equiv), [Cu(dap)2]Cl (8.8 mg, 1.0 μmol, 1.0 mol %), K2HPO4 (352 mg, 2.0 mmol, 2.0 equiv), and CF3SO2Cl (210 μL, 2.0 mmol, 2.0 equiv) in anhydrous MeCN (3 mL). The reaction solution was filtered through a silica plug with CH2Cl2 as the eluent. The filtrate was concentrated under reduced pressure to

was concentrated under reduced pressure to afford 4c as a colorless oil (207 mg, 94%). Following GP-B, 4c was prepared using pent-4en-1-ol 3c (510 μL, 5.0 mmol, 1.0 equiv), [Cu(dap)2]Cl (44 mg, 5.0 μmol, 1.0 mol %), K2HPO4 (1.76 g, 10.0 mmol, 2.0 equiv), CF3SO2Cl (1.1 mL, 10.0 mmol, 2.0 equiv), and dry MeCN (15 mL). The residue was purified by distillation under reduced pressure (0.7 mbar, oil bath temperature 120 °C, boiling point at 83−84 °C) to yield 4c as a colorless oil (7.72 g, 71%): Rf = not determinable; staining = not determinable (UV inactive); 1H NMR (600 MHz, CDCl3) δ = 4.61 (td, J = 11.1, 2.9 Hz, 1H), 4.55 (dtd, J = 11.4, 4.2, 1.8 Hz, 1H), 3.40 (tt, J = 10.6, 3.5 Hz, 1H), 2.94 (dqd, J = 15.3, 11.1, 2.9 Hz, 1H), 2.50−2.38 (m, 2H), 2.11 (dtd, J = 14.4, 10.9, 3.7 Hz, 1H), 2.03−1.95 (m, 1H), 1.90 (ddq, J = 15.2, 5.2, 3.5 Hz, 1H); 19 F NMR (282 MHz, CDCl3) δ = −63.86 (s, 3F); 13C NMR (75 MHz, CDCl3) δ = 125.4 (q, JC−F = 277.2 Hz), 74.5, 53.7 (q, JC−F = 2.3 Hz), 32.5 (q, JC−F = 30.8 Hz), 28.3, 23.2; IR (neat, cm−1) 2987, 1439, 1353, 1327, 1252, 1223, 1170, 1133, 1062, 1014, 939, 872, 794, 738; HRMS (ESI) exact mass calcd for C6H13F3NO3S m/z 236.0563, found m/z 236.0565 [M + NH4]+; GC analysis, purity 95%, tR = 7.103 min, wt(H2O) = 134 ppm. 3-(2,2,2-Trifluoroethyl)-1,2-oxathiepane 2,2-dioxide 4d. Following GP-A, 4d was prepared using hex-5-en-1-ol 3d (120 μL, 1.0 mmol, 1.0 equiv), [Cu(dap)2]Cl (8.8 mg, 1.0 μmol, 1.0 mol %), K2HPO4 (352 mg, 2.0 mmol, 2.0 equiv), and CF3SO2Cl (210 μL, 2.0 mmol, 2.0 equiv) in anhydrous MeCN (3 mL). The reaction solution was filtered through a silica plug with CH2Cl2 as the eluent. The filtrate was concentrated under reduced pressure to afford 3d as a colorless oil (74 mg, 32%); Rf = not determinable; staining = not determinable (UV inactive); 1H NMR (300 MHz, CDCl3) δ = 4.45−4.23 (m, 2H), 3.50−3.39 (m, 1H), 3.06−2.87 (m, 1H), 2.52− 2.31 (m, 1H), 2.30−2.18 (m, 1H), 2.16−2.05 (m, 2H), 2.05−1.92 (m, 1H), 1.86−1.66 (m, 2H); 19F NMR (282 MHz, CDCl3) δ = −63.89 (s, 3F); 13C NMR (75 MHz, CDCl3) δ = 125.7 (q, JC−F = 277.4 Hz), 71.1, 57.7 (q, JC−F = 2.2 Hz), 34.1 (q, JC−F = 30.2 Hz), 28.9, 28.5, 22.8; IR (neat, cm−1) 2961, 2923, 2853, 1458, 1357, 1261, 1133, 1096, 1022, 800, 633; HRMS (APCI) exact mass calcd for C7H11F3O3S m/z 233.0454, found m/z 233.0450 [M + H]+. 6,6-Dimethyl-3-(2,2,2-trifluoroethyl)-1,2-oxathiane 2,2-dioxide 4e. Following GP-A, 4e was prepared using 2-methylhex-5-en-2-ol 3e (115 mg, 1.0 mmol, 1.0 equiv), [Cu(dap)2]Cl (8.8 mg, 1.0 μmol, 1.0 mol %), K2HPO4 (352 mg, 2.0 mmol, 2.0 equiv), and CF3SO2Cl (210 μL, 2.0 mmol, 2.0 equiv) in anhydrous MeCN (3 mL). The reaction solution was filtered through a silica plug with CH2Cl2 as the eluent. The filtrate was concentrated under reduced pressure to afford 4e as a yellowish solid (179 mg, 73%): Rf = not determinable; staining = not determinable (UV inactive); 1H NMR (600 MHz, CDCl3) δ = 3.27 (tt, J = 10.7, 3.4 Hz, 1H), 2.97−2.89 (m, 1H), 2.40 (ddt, J = 15.2, 12.6, 10.0 Hz, 2H), 2.26−2.19 (m, 1H), 1.94 (ddd, J = 15.2, 11.8, 3.6 Hz, 1H), 1.87 (ddd, J = 14.7, 5.5, 3.4 Hz, 1H), 1.63 (s, 3H), 1.53 (s, 3H); 19F NMR (376 MHz, CDCl3) δ = −63.59 (s, 3F); 13C NMR (101 MHz, CDCl3) δ = 125.6 (q, JC−F = 277.3 Hz), 93.2, 52.6 (q, JC−F = 2.3 Hz), 35.1, 32.6 (q, JC−F = 30.4 Hz), 30.4, 25.4, 25.1 (dd, JC−F = 2.5, 1.1 Hz); IR (neat, cm−1) 2994, 2955, 1446, 1396, 1342, 1291, 1243, 1174, 1132, 1097, 1078, 1032, 875, 848, 778, 696, 545; HRMS (ESI) exact mass calcd for C8H14F3O3S m/z 247.0610, found m/z 247.0611 [M + H]+; mp 68−71 °C. 5,5-Diphenyl-3-(2,2,2-trifluoroethyl)-1,2-oxathiane 2,2-dioxide 4f. Following GP-A, 4f was prepared using 2,2-diphenylpent-4-en1-ol 3f (238 mg, 1.0 mmol, 1.0 equiv), [Cu(dap)2]Cl (8.8 mg, 1.0 μmol, 1.0 mol %), K2HPO4 (352 mg, 2.0 mmol, 2.0 equiv), and CF3SO2Cl (210 μL, 2.0 mmol, 2.0 equiv) in anhydrous MeCN (3 mL). Chromatography on silica gel (pentane/CH2Cl2, 2:1) afforded 4f as a white solid (269 mg, 73%): Rf (pentane/CH2Cl2, 3:1) = 0.25; staining = PMA (UV active); 1H NMR (600 MHz, CDCl3) δ = 7.45−7.24 (m, 8H), 7.13−7.07 (m, 2H), 5.04 (dd, J = 12.3, 2.7 Hz, 1H), 4.79 (d, J = 12.4 Hz, 1H), 3.22 (tdd, J = 10.5, 4.8, 2.8 Hz, 1H), 3.12−3.02 (m, 2H), 2.87 (dqd, J = 15.2, 10.9, 2.8 Hz, 1H), 2.51− 2.42 (m, 1H); 19F NMR (376 MHz, CDCl3) δ = −63.22 (s, 3F); 13 C NMR (101 MHz, CDCl3) δ = 141.4, 140.3, 129.4, 129.1, 128.0, 127.9, 127.6, 127.1, 125.4 (d, JC−F = 277.5 Hz), 78.4, 50.9 (q, JC−F = 7144

DOI: 10.1021/acs.joc.6b01001 J. Org. Chem. 2016, 81, 7139−7147

Article

The Journal of Organic Chemistry afford 4j as a yellowish oil (178 mg, 67% yield): Rf (pentane/ CH2Cl2, 3:1) = 0.20; staining = PMA (UV active); 1H NMR (300 MHz, CDCl3) δ = 7.39−7.05 (m, 4H), 3.83 (dddd, J = 10.8, 8.0, 5.3, 2.6 Hz, 1H), 3.70 (dd, J = 17.0, 5.4 Hz, 1H), 3.41 (dd, J = 17.1, 8.3 Hz, 1H), 3.09 (dqd, J = 15.1, 10.8, 2.6 Hz, 1H), 2.61−2.43 (m, 1H); 19 F NMR (282 MHz, CDCl3) δ = −63.81 (s, 3F); 13C NMR (75 MHz, CDCl3) δ = 151.1, 129.9, 129.2, 126.2, 125.4 (q, JC−F = 277.3 Hz), 119.3, 118.9, 50.4 (q, JC−F = 2.6 Hz), 32.5 (q, JC−F = 28.9 Hz), 32.3; IR (neat, cm−1) 3071, 2960, 1618, 1584, 1457, 1491, 1375, 1327, 1260, 1186, 1148, 1096, 1010, 924, 876, 816, 790, 757, 719, 670; HRMS (EI) exact mass calcd for C10H9F3O3S m/z 266.0219, found m/z 266.0208 [M]+; GC analysis, purity 89%, tR = 10.411 min. 6-Phenyl-3-(2,2,2-trifluoroethyl)-1,2-oxathiane 2,2-Dioxide 4k. Following GP-A, 4k was prepared using 1-phenylpent-4-en-1-ol 3k (150 mg, 0.9 mmol, 1.0 equiv), [Cu(dap)2]Cl (8.1 mg, 1.0 μmol, 1.0 mol %), K2HPO4 (320 mg, 1.8 mmol, 2.0 equiv), and CF3SO2Cl (195 μL, 1.8 mmol, 2.0 equiv) in anhydrous MeCN (2.5 mL). Chromatography on silica gel (hexanes/EtOAc, 5:1) afforded 4k as a colorless liquid (181 mg, 67%): Rf (hexanes/EtOAc, 7:3) = 0.4; staining = anisaldehyde (UV active); 1H NMR (300 MHz, CDCl3) δ = 7.34 (tdd, J = 9.3, 6.6, 4.3 Hz, 6H), 7.23 (td, J = 7.7, 1.8 Hz, 4H), 4.90−4.74 (m, 2H), 3.56 (dddd, J = 11.6, 10.3, 7.3, 4.1 Hz, 1H), 3.29−3.18 (m, 2H), 3.17−3.02 (m, 2H), 3.01−2.76 (m, 3H), 2.75− 2.67 (m, 1H), 2.57−2.30 (m, 4H), 2.22−2.10 (m, 1H); 19F NMR (282 MHz, CDCl3) δ = −64.93 (s, 3F), −64.97 (s, 3F); 13C NMR (75 MHz, CDCl3) δ = 134.5, 134.3, 129.6, 129.4, 129.1, 129.0, 127.8, 127.7, 125.2 (q, JC−F = 277.2 Hz), 81.3, 79.9, 52.1 (q, JC−F = 2.9 Hz), 49.8 (q, JC−F = 2.9 Hz), 41.1, 41.1, 35.7, 33.2 (q, JC−F = 7.4 Hz); IR (neat, cm−1) 3068, 3034, 2956, 1609, 1498, 1454, 1394, 1349, 1320, 1260, 1163, 1077, 1033, 992, 842, 753; HRMS (ESI) exact mass calcd for C12H14F3O3S m/z 294.0700, found m/z 294.0611 [M + H]+. 8-Methoxy-3-(2,2,2-trifluoroethyl)-3,4-dihydrobenzo[e][1,2]oxathiine 2,2-Dioxide 4m. Following GP-A, 4m was prepared using 2-allyl-6-methoxyphenol 3m (492 mg, 3.0 mmol, 1.0 equiv), [Cu(dap)2]Cl (26 mg, 3.0 μmol, 1.0 mol %), K2HPO4 (1.06 g, 6.0 mmol, 2.0 equiv), and CF3SO2Cl (630 μL, 6.0 mmol, 2.0 equiv) in anhydrous MeCN (9 mL). Chromatography on silica gel (pentane/CH2Cl2, 7:1) afforded 4m as a yellowish solid (566 mg, 64%): Rf (hexanes/EtOAc, 5:1) = 0.36; staining = anisaldehyde (UV active); 1H NMR (300 MHz, CDCl3) δ = 7.13 (t, J = 8.0 Hz, 1H), 6.89 (dd, J = 8.4, 1.4 Hz, 1H), 6.81−6.75 (m, 1H), 3.86 (d, J = 1.5 Hz, 3H), 3.78 (ddt, J = 10.6, 5.3, 2.6 Hz, 1H), 3.66 (dd, J = 17.2, 5.4 Hz, 1H), 3.36 (dd, J = 17.1, 8.0 Hz, 1H), 3.12−2.96 (m, 1H), 2.56− 2.39 (m, 1H); 19F NMR (282 MHz, CDCl3) δ = −63.84 (s, 3F); 13 C NMR (75 MHz, CDCl3) δ = 149.0, 140.5, 126.0, 125.4 (q, JC−F = 277.6 Hz), 120.8, 120.5, 111.5, 56.2, 50.3 (q, JC−F = 2.6 Hz), 32.6 (q, JC−F = 30.8 Hz), 32.4; IR (neat, cm−1) 3019, 2982, 2948, 2844, 1618, 1588, 1480, 1372, 1323, 1279, 1204, 1144, 1111, 999, 954, 869, 801, 716, 686; HRMS (ESI) exact mass calcd for C11H11F3O4S m/z 296.0325, found m/z 296.0319 [M]+; mp 97−100 °C. 3-(2,2,3,3,4,4,5,5,5-Nonafluoropentyl)-1,2-oxathiane 2,2-Dioxide 5a. Following GP-A, 5a was prepared using pent-4-en-1-ol 3c (102 μL, 1.0 mmol, 1.0 equiv), [Cu(dap)2]Cl (8.8 mg, 1.0 μmol, 1.0 mol %), K2HPO4 (352 mg, 2.0 mmol, 2.0 equiv), and perfluorobutanesulfonyl chloride (636 mg, 2.0 mmol, 2.0 equiv) in anhydrous MeCN (3 mL). The reaction solution was filtered through a silica plug with CH2Cl2 as the eluent. The filtrate was concentrated under reduced pressure to afford 5a as a white solid (162 mg, 44%): Rf = not determinable; staining = not determinable (UV inactive); 1H NMR (300 MHz, CDCl3) δ = 4.70−4.49 (m, 2H), 3.52 (tdd, J = 10.3, 3.9, 2.7 Hz, 1H), 3.01−2.79 (m, 1H), 2.54−2.26 (m, 2H), 2.22−2.11 (m, 1H), 2.11−1.96 (m, 1H), 1.91 (dtt, J = 11.2, 5.4, 3.0 Hz, 1H); 19F NMR (282 MHz, CDCl3) δ = −81.56 (td, J = 9.6, 4.9 Hz, 3F), −109.36 to −117.15 (m, 2F), 124.74 (tq, J = 9.5, 4.7, 4.2 Hz, 2F), −126.42 (dtd, J = 24.7, 13.1, 12.1, 4.5 Hz, 2F); 13C NMR (75 MHz, CDCl3) δ = 74.6, 53.0 (d, JC−F = 3.9 Hz), 29.4 (t, JC−F = 21.9 Hz), 29.1 (d, JC−F = 3.7 Hz), 23.5; IR (neat, cm−1) 3088, 3031, 2996, 2962, 1600, 1584, 1497, 1448, 1376, 1337, 1227, 1193, 1172, 1133,

1111, 1081, 971, 931, 802, 738, 696, 513; HRMS (ESI) exact mass calcd for C9H10F9O3S m/z 369.0201, found m/z 369.0200 [M + H]+; mp 66−68 °C. 3-(2,2,3,3,4,4,5,5,5-Nonafluoropentyl)-5,5-diphenyl-1,2-oxathiane 2,2-Dioxide 5b. Following GP-A, 5b was prepared using 2,2diphenylpent-4-en-1-ol 3f (238 mg, 1.0 mmol, 1.0 equiv), [Cu(dap)2]Cl (8.8 mg, 1.0 μmol, 1.0 mol %), K2HPO4 (352 mg, 2.0 mmol, 2.0 equiv), and perfluorobutanesulfonyl chloride (636 mg, 2.0 mmol, 2.0 equiv) in anhydrous MeCN (3 mL). Chromatography on silica gel (pentane/CH2Cl2, 2:1) afforded 5b as a white solid (218 mg, 41%): Rf (pentane/CH2Cl2, 3:1) = 0.29; staining = PMA (UV active); 1H NMR (600 MHz, CDCl3) δ = 7.47−7.24 (m, 8H), 7.15− 7.06 (m, 2H), 5.06 (dd, J = 12.4, 2.8 Hz, 1H), 4.82 (d, J = 12.4 Hz, 1H), 3.34 (tdd, J = 10.3, 4.8, 2.5 Hz, 1H), 3.17−3.05 (m, 2H), 2.86 (dddd, J = 33.1, 16.9, 6.4, 2.4 Hz, 1H), 2.49−2.38 (m, 1H); 19F NMR (282 MHz, CDCl3) δ = −81.50 (td, J = 9.7, 4.8 Hz, 3F), 105.42−118.36 (m, 2F), −124.69 (dt, J = 11.4, 4.4 Hz, 2F), −126.41 (ddd, J = 26.1, 16.5, 11.8 Hz, 2F); 13C NMR (75 MHz, CDCl3) δ = 141.4, 140.2, 129.4, 129.1, 128.0, 127.9, 127.6, 127.0, 78.4, 50.1 (d, JC−F = 3.7 Hz), 47.7, 40.3 (d, JC−F = 3.6 Hz), 29.2 (t, JC−F = 21.6 Hz); IR (neat, cm−1) 2951, 2931, 2868, 2332, 2164, 2053, 1435, 1385, 1350, 1292, 1276, 1221, 1188, 1166, 1131, 1072, 1040, 1023, 1008, 931, 877, 855, 808, 786, 741, 696, 513; HRMS (ESI) exact mass calcd for C21H18F9O3S m/z 521.0827, found m/z 521.0825 [M + H]+; mp 111−115 °C. 8-Hydroxy-3-(2,2,2-trifluoroethyl)-3,4-dihydrobenzo[e][1,2]oxathiine 2,2-Dioxide 8. A mixture of 8-methoxy-3-(2,2,2-trifluoroethyl)-3,4-dihydrobenzo[e][1,2]oxathiine 2,2-dioxide 4m (500 mg, 1.7 mmol, 1.0 equiv) and hydrobromic acid (30 mL, 47 wt %) was heated at 140 °C for 3 h. After completion of the reaction as monitored by TLC, the mixture was cooled to room temperature and extracted with Et2O (3 × 30 mL). The combined organic layers were washed with once with brine (1 × 50 mL), dried over anhydrous Na2SO4, and concentrated under reduced pressure. The residue was recrystallized from pentane/CH2Cl2 (1:1) to obtain product 8 as a white solid (470 mg, 99%): Rf (hexanes/EtOAc, 5:1) = 0.32; staining = anisaldehyde (UV active); 1H NMR (300 MHz, CDCl3) δ = 7.10 (t, J = 7.9 Hz, 1H), 6.96 (dd, J = 8.2, 1.5 Hz, 1H), 6.76 (dt, J = 7.8, 1.2 Hz, 1H), 5.43 (s, 1H), 3.85 (dddd, J = 10.7, 8.0, 5.2, 2.6 Hz, 1H), 3.68 (dd, J = 17.0, 5.2 Hz, 1H), 3.40 (dd, J = 17.2, 8.1 Hz, 1H), 3.13−2.99 (m, 1H), 2.52 (ddt, J = 15.1, 10.7, 9.6 Hz, 1H); 19F NMR (282 MHz, CDCl3) δ = −63.80 (s, 3F); 13C NMR (75 MHz, CDCl3) δ = 145.1, 139.2, 126.5, 125.3 (q, JC−F = 277.3 Hz), 120.7, 119.9, 116.1, 51.0 (q, JC−F = 2.3 Hz), 32.6 (q, JC−F = 31.0 Hz), 32.4; IR (neat, cm−1) 3452, 2922, 2851, 2117, 1946, 1737, 1633, 1592, 1502, 1476, 1394, 1361, 1320, 1267, 1118, 1006, 939, 895, 790, 682; HRMS (EI) exact mass calcd for C10H9F3O4S m/z 282.0168, found m/z 282.0166 [M]+; mp 112−114 °C. 8-(Oxiran-2-ylmethoxy)-3-(2,2,2-trifluoroethyl)-3,4-dihydrobenzo[e][1,2]oxathiine 2,2-Dioxide 9. To a solution of 8 (400 mg, 1.4 mmol, 1.0 equiv) and epichlorohydrin (2 mL, 25.5 mmol, 18.2 equiv) in acetone (20 mL) was added K2CO3 (433 mg, 3.1 mmol, 2.2 equiv), and the mixture was heated at reflux for 2 days. Afterward, the solvent was removed in vacuo and the residue extracted with CHCl3 (3 × 50 mL). The combined organic layers were washed with water (1 × 50 mL) followed by brine (1 × 50 mL), dried over anhydrous Na2SO4, and concentrated under reduced pressure. The residue was purified by chromatography on silica gel (CH2Cl2) to afford 9 as a white solid (312 mg, 65%) in a diastereomeric mixture of syn/anti = 50:50: Rf (CH2Cl2) = 0.43; staining = KMnO4 (UV active); 1H NMR (400 MHz, CDCl3) δ = 7.12 (t, J = 8.0 Hz, 1H), 6.94 (dd, J = 8.3, 1.3 Hz, 1H), 6.81 (dd, J = 7.8, 1.2 Hz, 1H), 4.28 (dt, J = 11.3, 2.7 Hz, 1H), 4.02 (ddd, J = 11.3, 5.5, 2.2 Hz, 1H), 3.79 (dddt, J = 10.4, 7.8, 5.0, 2.4 Hz, 1H), 3.66 (dd, J = 17.0, 5.4 Hz, 1H), 3.47−3.31 (m, 2H), 3.06 (dqd, J = 15.2, 10.8, 2.6 Hz, 1H), 2.91 (t, J = 4.5 Hz, 1H), 2.77 (ddd, J = 4.9, 2.7, 0.9 Hz, 1H), 2.59−2.38 (m, 1H); 19F NMR (376 MHz, CDCl3) δ = −63.84 (s, 3F), −63.85 (s, 3F); 13C NMR (101 MHz, CDCl3) δ = 148.1, 148.1, 141.1, 126.1, 125.4 (q, JC−F = 277.5 Hz), 121.7, 121.7, 120.8, 120.8, 113.7, 113.7, 70.4, 70.3, 50.4 (ddd, JC−F = 5.4, 2.6, 1.5 7145

DOI: 10.1021/acs.joc.6b01001 J. Org. Chem. 2016, 81, 7139−7147

Article

The Journal of Organic Chemistry Hz), 50.3 (ddd, JC−F = 5.8, 2.6, 1.3 Hz), 50.1, 44.8, 44.8, 32.6 (q, JC−F = 28.0 Hz), 32.2 (q, JC−F = 28.0 Hz), 32.5, 32.5; IR (neat, cm−1) 3097, 3004, 2933, 1621, 1588, 1480, 1372, 1327, 1267, 1193, 1152, 1118, 1010, 939, 887, 790, 719; HRMS (ESI) exact mass calcd for C13H17F3NO5S m/z 356.0774, found m/z 356.0777 [M + NH4]+; mp 80−81 °C. 8-(3-(tert-Butylamino)-2-hydroxypropoxy)-3-(2,2,2-trifluoroethyl)-3,4-dihydrobenzo[e][1,2]oxathiine 2,2-Dioxide 10. To a solution of 9 (200 mg, 0.6 mmol, 1.0 equiv) in anhydrous MeOH (40 mL) was added freshly distilled tert-butylamine (0.8 mL, 7.7 mmol, 12.9 equiv), and the mixture was heated at reflux for 2 h. Afterward, the solvent and the amine were removed in vacuo. The residue was purified by chromatography on silica gel (CH2Cl2) followed by recrystallization from pentane/CH2Cl2 (1:1) to obtain product 10 as a white solid (202 mg, 49%) in a diastereomeric mixture of syn/anti = 50:50: Rf (CH2Cl2) = 0.13; staining = KMnO4 (UV active); 1H NMR (600 MHz, CDCl3) δ = 7.10 (t, J = 7.9 Hz, 1H), 6.92 (d, J = 8.0 Hz, 1H), 6.79 (d, J = 7.7 Hz, 1H), 4.27 (dt, J = 7.4, 3.4 Hz, 1H), 4.19 (td, J = 9.0, 8.5, 4.4 Hz, 1H), 4.09−4.02 (m, 2H), 3.77 (dtd, J = 10.7, 7.9, 5.1 Hz, 2H), 3.63 (dd, J = 17.0, 5.4 Hz, 1H), 3.37−3.33 (m, 1H), 3.10 (dt, J = 12.2, 3.3 Hz, 1H), 3.05−2.97 (m, 1H), 2.47 (ddd, J = 24.9, 19.5, 9.6 Hz, 2H), 1.28 (s, 9H); 19F NMR (376 MHz, CDCl3) δ = −63.82 (s, 3F), 63.84 (s, 3F); 13C NMR (151 MHz, CDCl3) δ = 148.0, 140.8, 140.7, 126.0, 125.2 (q, JC−F = 277.4 Hz), 121.4, 121.3, 120.6, 120.6, 113.4, 113.4, 73.9, 73.8, 71.8, 71.7, 50.4−50.2 (m), 44.7, 44.7, 32.5 (q, JC−F = 30.9 Hz), 32.4, 27.2, 25.7; IR (neat, cm−1) 3327, 2971, 2937, 2873, 2618, 1742, 1618, 1585, 1477, 1379, 1322, 1271, 1236, 1192, 1155, 1119, 1039, 1009, 945, 886, 841, 784, 769, 732, 664, 623, 581, 548; HRMS (ESI) exact mass calcd for C17H24F3NO5S m/z 412.1400, found m/z 412.1404 [M + H]+; mp 88−89 °C. 3-(2,2,2-Trifluoroethyl)-1,2-oxathiane 2,2-Dioxide 15. Following GP-A, 15 was prepared using 5-methoxypent-1-ene 14 (100 mg, 1.0 mmol, 1.0 equiv), [Cu(dap)2]Cl (8.8 mg, 1.0 μmol, 1.0 mol %), K2HPO4 (352 mg, 2.0 mmol, 2.0 equiv), and CF3SO2Cl (210 μL, 2.0 mmol, 2.0 equiv) in anhydrous MeCN (3 mL). Chromatography on silica gel (pentane/Et2O, 5:1) afforded 15 as a colorless oil (150 mg, 56%): Rf (pentane/Et2O, 5:1) = 0.45; staining = KMnO4 (UV inactive); 1H NMR (300 MHz, CDCl3) δ = 3.93 (dtd, J = 8.7, 5.8, 2.7 Hz, 1H), 3.44 (td, J = 5.9, 2.2 Hz, 2H), 3.33 (s, 3H), 3.07 (dqd, J = 15.5, 10.5, 2.7 Hz, 1H), 2.67−2.48 (m, 1H), 2.31 (dq, J = 14.4, 7.2 Hz, 1H), 2.12 (dtd, J = 15.1, 7.2, 6.7, 5.1 Hz, 1H), 1.91−1.81 (m, 2H); 19F NMR (282 MHz, CDCl3) δ = −64.22 (s, 3F); 13C NMR (75 MHz, CDCl3) δ = 125.0 (q, JC−F = 277.2 Hz), 71.7, 69.7 (q, JC−F = 2.3 Hz), 58.8, 35.0 (q, JC−F = 30.9 Hz), 28.1, 26.2; IR (neat, cm−1) 2933, 2881, 2837, 1439, 1372, 1320, 1260, 1156, 1118, 1070, 1029, 902, 842, 772; HRMS (CI+) exact mass calcd for C7H13ClF3O3S m/z 269.0221, found m/z 269.0220 [M + H]+.

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(Fellowships for E.L.). The authors also thank Dr. Michael Bodensteiner and Katharina Beier, Universität Regensburg, for carrying out the X-ray crystal structure analysis.

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S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.joc.6b01001. Copies of 1H, 13C, and 19F NMR spectra and GC−MS spectra for all compounds (PDF) X-ray crystallographic data for sultone 4f (CIF)

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REFERENCES

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the DFG (Graduiertenkolleg 1626 Photocatalysis) as well as by the Studienstiftung des Deutschen Volkes and Fonds der Chemischen Industrie 7146

DOI: 10.1021/acs.joc.6b01001 J. Org. Chem. 2016, 81, 7139−7147

Article

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DOI: 10.1021/acs.joc.6b01001 J. Org. Chem. 2016, 81, 7139−7147